Research on MOF as well as carbon nano morphologies like carbon nanotubes (CNTs), graphene (GE) and carbon nanofibers (CNFs) has picked up attention due to variety of applications like gas storage, sensing, drug delivery and catalysis.
The large void space generated by cages in MOFs is not completely utilized for hydrogen or other gas storage applications owing to weak interactions between the walls of MOFs and H2 molecules. These unutilized volumes in MOFs can be effectively utilized by incorporation of other microporous materials such as single walled carbon nanotubes into the pores of MOFs which could effectively tune the pore size and pore volume of the material towards hydrogen sorption. Also, efforts are on to improve the properties of both MOFs as well as nano carbon morphologies. Specific examples of projects undertaken in MOFs aim at increasing and controlling functionality, introduction of exposed metal sites, doping the MOFs with alkali metal ions and such others. Similarly, for nano carbon morphologies, various strategies like surfactant encapsulation, polymer wrapping and attachment of various metal and metal oxide nanoparticles have been attempted.
References may be made to Patent EP1513612, which discloses a porous metal-organic framework, which can be used to store gases, such as hydrogen. The invention further provides a metal-organic framework comprising organic functional groups directed into the one or more cavities that are capable of reacting with a storage gas. It further provides method by which a novel group of MOFs is prepared by inverting the structural role of the Secondary Building Unit (SBU) and linear organic bridge such that the SBU serve as a linear bridge and the organic ligand serves as a node.
References may be made to Journal. Angewandte Chemie International Edition Volume 50, Issue 2, pages 491-494, Jan. 10, 2011, wherein Zhonghua Xia et. al have reported that the gas storage capacities of metal-organic frameworks can be increased by incorporation of carbon nanotubes and doping of the resulting framework with lithium ions. The combination they have suggested cause improvement of the CO2 and CH4 uptakes by about 305% and 200% respectively.
References may be made to Journal International Journal of Hydrogen Energy, Volume 36, Issue 13, July 2011, Pages 7594-7601, wherein K. P. Prasanth et. al. have reported synthesis of Single walled carbon nanotubes (SWNT) and MOF composite by adding purified SWNT in situ during the synthesis of composite. Hydrogen sorption capacities of MIL-101 was observed to increase from 6.37 to 9.18 wt % at 77 K up to 60 bar and from 0.23 to 0.64 wt % at 298 K up to 60 bar. The increment in the hydrogen uptake capacities of composite MOF materials was attributed to the decrease in the pore size and enhancement of micropore volume of MIL-101 by single walled carbon nanotube incorporation.
Despite the recent progresses in the construction of novel MOF-nano carbon hybrid structures through different strategies and improvement in the sorption capabilities of such hybrids, the nature of interaction between the MOF and nanocarbon components still possesses a limitation to the versatile exploration of such hybrids. Also, most of the hybrids are physical mixtures and they lack proper chemical interactions between the individual counterparts.
To achieve the desired properties and synergies of the hybrid composite of MOFs and carbon nano morphologies, mere physical mixing is not the desired process of making them. But, the modifications in the properties by synergistic effects need chemical interactions such that they result in novel hybrids of MOFs and nano carbon morphologies with modulated properties with synergistic effects.
To overcome the disadvantages of the prior art and to provide solution to the long standing problems, the inventors have come up with novel hybrids of MOFs and nano carbon morphologies.